Atari STe Video Switch

This is a low-cost analog video switch for Atari STe, to select between Atari 13-pin DIN video output, VGA color output, and VGA mono output.  The original Atari video modes are output as-is, so you'll likely need a multisync monitor to utilise the VGA color output mode.

Analog red, green, blue, and monochrome video signals are switched using three TI THS7374 video amplifiers (in filter bypass mode).  Horizontal and vertical sync signals are buffered and switched using two TI SN74LVC2G241 dual buffer/drivers.  Monochrome mode selection is switched using two TI TS5A3159DBVR analog switches.  Composite video is always available on a separate RCA connector, and audio is always routed to/from the output 13-pin DIN connector only.

Mode selection uses a single-pole three-throw (SP3T) switch.  The one in the schematic is a DP3T, but only one half of it is used.  Because of the video amplifiers and sync buffers, both DIN and VGA outputs could be used simultaneously; the current schematic simply disables the other output.

This is an untested, unverified schematic, created as part of this discussion at EEVblog forums.